1. Technical Field
The present invention relates generally to network devices and more particularly to network device continuity.
2. Description of Related Art
One goal of communication networks is to have constant availability and accessibility of network devices such as servers and databases. When the operations of the network devices are mission critical, constant availability and accessibility becomes even more important. Unfortunately, the network devices do become unavailable for some period of time due to routine maintenance, hardware or software failures, or sub-standard performance.
In order to provide fault tolerance, some network devices are designed to handle these periods of unavailability. In one example, as soon as a network device becomes unavailable, the network device diverts traffic to a backup device or other available network devices. The switching of traffic to other network device should be automatic and immediate to ensure a transition transparent to the user or originating device.
FIG. 1 depicts an illustration of a communication network in a bridge configuration in the prior art. The computers 110, 120, 130 and the local area network (LAN) switch 140 form a LAN. The network device 150 is coupled between the LAN and the wide area network (WAN) router 160 and acts essentially as a bridge between the LAN and the WAN 170. In this example, the network device 150 includes a spring-loaded electromechanical mechanism 152 attached to the communication links 154 and 156. In a “fail-to-wire” scenario, when the network device 150 fails, the spring-loaded electromechanical mechanism 152 shuts the communication links 154 and 156 and the network device 150 behaves as a straight wire. One problem is when the network device 150 fails, the traffic between the LAN and the WAN 170 is interrupted while the network device 150 is replaced or corrected. Another problem is that some prior art “fail-to wire” network devices are in the Open System Interconnection (OSI) layer 2 and layer 3, which is a mixed solution that may be non-standard.
One problem with some network devices is that when there is a software error in the network device, the network device remains coupled to the communication network. For example, when a processor in the network device is in an infinite loop, the network device remains coupled to the communication network, and the communications continue to be sent to the network device from the communication network.
Other communication networks include policy based routers that route traffic based on policies set up by network administrators. One limitation of some of these policy based routers is that communication protocols and control of the policy based routers are proprietary to the manufacturer of the policy based routers. Thus, other network devices attached to the policy based routers cannot control routing through the policy based routers in a failure or maintenance scenario. One example of a communications protocol is Cisco Discovery Protocol from Cisco Systems, Inc. in San Jose, Calif. The communication protocols and control of the policy based routers may not be available to other vendors, or the policy based routers do not have the proper interfaces for control communications with other network devices. Furthermore, licensing the technology of the communication protocols and control may not be a cost effective solution.